1. Field of the Invention
The present invention relates to a printhead substrate, a method of manufacturing the same, a printhead, and a printing apparatus.
2. Description of the Related Art
On a printhead substrate for performing inkjet printing, an electrothermal transducer for heating ink (printing material), and a temperature detection element for detecting the temperature of the electrothermal transducer can be provided.
Japanese Patent Laid-Open No. 2009-248517 discloses a printhead substrate on which a temperature detection element is formed on an insulating member (heat storage layer) on a silicon substrate, and an electrothermal transducer is formed on an interlayer insulating film on the temperature detection element. In addition to the temperature detection element, a plurality of wiring patterns which include electrodes connected to the temperature detection element are formed on the insulating member. According to Japanese Patent Laid-Open No. 2009-248517, after a metal member is formed on the insulating member to cover the plurality of wiring patterns, this metal member is patterned by etching, thereby forming the temperature detection element connected to the electrodes.
By performing over-etching (etching whose etching amount is larger than the thickness of the metal member) when etching the above-described metal member, the short circuit of the plurality of wiring patterns due to a residue which is caused by the etching can be prevented. However, if the etching amount of the over-etching is larger than necessary, a large step is formed on the upper surface of a structure in which the temperature detection element after the etching is formed. This step has an influence on the shape of the electrothermal transducer. For example, it impairs the flatness of the electrothermal transducer to be formed on the temperature detection element later. As a result, a decrease in the electrothermal transduction efficiency of the electrothermal transducer may occur.